is there a way to check if a bash script is complete or not?

Question

I\'m trying to implement a REPL (read-eval-print loop) in bash. If such a thing already exists, please ignore the following and answer this question with a pointer to it.

Answer 1

Assume your test commands are stored in a file called "example". That is, using same commands than in previous answer:

$ cat example
x=3
echo "$x"
y=$(($x+1))
echo "$y"


while [ "$y" -gt "0" ]
do
    echo $y
    y=$(($y-1))
done

the command:

$ (echo 'PS1=; PROMPT_COMMAND="echo -n =====; echo"'; cat example2 ) | bash -i

produces:

=====
x=3
=====
echo "$x"
3
=====
y=$(($x+1))
=====
echo "$y"
4
=====

=====

=====
while [ "$y" -gt "0" ]
> do
>     echo $y
>     y=$(($y-1))
> done
4
3
2
1
=====
exit

if you are interested also in the intermediate results of a loop, the command:

$ ( echo 'trap '"'"'echo; echo command: $BASH_COMMAND; echo answer:'"'"' DEBUG'; cat example ) | bash

results in:

command: x=3
answer:

command: echo "$x"
answer:
3

command: y=$(($x+1))
answer:

command: echo "$y"
answer:
4

command: [ "$y" -gt "0" ]
answer:

command: echo $y
answer:
4

command: y=$(($y-1))
answer:

command: [ "$y" -gt "0" ]
answer:

command: echo $y
answer:
3

command: y=$(($y-1))
answer:

command: [ "$y" -gt "0" ]
answer:

command: echo $y
answer:
2

command: y=$(($y-1))
answer:

command: [ "$y" -gt "0" ]
answer:

command: echo $y
answer:
1

command: y=$(($y-1))
answer:

command: [ "$y" -gt "0" ]
answer:

Addendum 1

It is not difficult to change the previous results to some other format. By example, this small perl script:

$ cat formatter.pl 
#!/usr/bin/perl
#

$state=4; # 0: answer, 1: first line command, 2: more command, 4: unknown

while(<>) {
#  print $state;

  if( /^===COMMAND===/ ) {
    print "===\n";
    $state=1;
    next;
  }

  if( $state == 1 ) {
    print;
    $state=2;
    next;
  }

  if( $state == 2 && /^>+ (.*)/ ) {
    print "$1\n";
    next;
  }

  if( $state == 2 ) {
    print "---\n";
    $state=0;
    redo;
  }

  if( $state == 0 ) {
    print;
    next;
  }
}

when used in command:

( echo 'PS1="===COMMAND===\n"'; cat example ) | bash -i 2>&1 | ./formatter.pl

gives this result:

===
x=3
===
echo "$x"
---
3
===
y=$(($x+1))
===
echo "$y"
---
4
===

===

===
while [ "$y" -gt "0" ]
do
    echo $y
    y=$(($y-1))
done
---
4
3
2
1
===
exit